So battery testing.

To test a battery properly, you need to take it off the car, charge it fully for 24 hours using an intelligent battery charger.

Place a load, like a headlamp bulb (12V 60W) across the terminals for 5 minutes. This removes the surface charge which give a falsely high reading. Leave the battery for a few hours. Take a volt reading with a digital multimeter.

The battery should give you a 100% charge reading as the below table - >12.7V. If it is less, the battery is near end of life.

The next test is to load it at C20 for 10 hours which means 1/20th of its rated capacity. So a 100AH battery, C20 is 5 Amps. Conveniently a 12V halogen headlamp of 60W. After 10 hours remove load and leave for 12 hours and take voltage. Ideally it will be around 12.2 Volts or more.

You will find slightly varying figures for this table. But you'll get a good sense from this test. If it falls to below 12V on this test, battery is ready to replace.

Never plan to take more than 50% of charge from a battery during testing - flooded cell will be damaged much below 50% level of charge. AGM and deep cycle can go further, but they don't like it either.

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Dartman the one wrote:

The voltage is fairly immaterial with intelligent charging systems and alternators, the current is what causes the damage, I suspect the current is limited to milli Amps when the battery is fully charged, there will be two circuits, the battery charging and a vehicle supply, if measuring at the cigar/ power socket then this could be a few milli volts higher than the battery voltage, but there again a cheap plug in voltmeter could well be up to 0.5 volts over or under reading.

npinks wrote:

interesting Bill, i'm sure they said my car had a smart alternator fitted when i queried the low voltage/dashcam turning off all the time, not had any issues with my caravan battery, that have become apparent, but is there a device that could be installed inline to prevent 18v hitting the caravan battery?

The Freelander does have intelligent charging with a smart alternator there was a problem with it charging caravan batteries in its early days and LR modified the charging circuit to overcome this problem.
Whether the FL2 charging current is constant current I don't know, most old systems had a maximum current limit which could be quite high, theoretically 14.4 volts would not give much of a charge so therefore the open circuit voltage must raise above 14.4 volts to get a decent charge though the on load voltage is 14.4 or in some cases 13.8v with other manufacturers. Th voltage can be anything, Wattless volts never hurt anything it's volts with current that causes problems or in other words power, you can't have current without volts but you can have volts without current.
Those that have tried will find that intelligent charger won't give out a voltage unless connected to a battery, that being so they are a pain in the neck as you can't use them as a 12v power source, many car handbooks state never to run the engine when the battery is disconnected as the voltage will fly high as it tries to produce a current. my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

"The voltage can be anything, Wattless volts never hurt anything it's volts with current that causes problems or in other words power, you can't have current without volts but you can have volts without current"

That is only true to a point - any 12V lead acid battery will starting drawing current once the charge voltage is above about 14.4 or 14.7V (std or AGM), even if fully charged. If there is no current available in the supply to sustain that voltage, the voltage won't rise any higher than that. If the supply tries to go to, say 18V, and there is also current (power) available, then you are in trouble - enough current for long enough and plates buckle, acid boils, all hell breaks loose!

In general 99% of cars will never do this - the 18V being spoken of sounds like a specific faulty implementation (I should check the link perhaps !!)

This is why those tiddly 5W (max) solar panels are safe on a battery - open circuit (no current drain), they can rise to perhaps 20V or more As soon as you stick them on a battery, they are pinned to the battery chemistry as they don't have enough power to raise the volts too high. They also have internal resistance. (Don't do this with a big 100W solar array - that can chuck enough current to boil the battery, you need a regulator for that)

My clamp meter showed after 20 seconds the alternator had increased to & settled at an 80amp charge. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

That's a lot of amps ! Hence why a car should charge when being used.

BTW, looking at your signature, why carpet in the doors?

To stop things rattling & sliding. I have only done the front pockets.

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Click image to enlarge

My 3.2 charging voltage varies considerably depending (I guess) on the state of the battery. It can go as high is 14 V and as low as 13.2V. I believe the 3.2 use a smart charging system so traditional plug in battery monitors aren't really that useful. The one I have shows voltage and has led's to indicate the state of the battery and any charging system faults. Last night during a longish drive the voltmeter showed 13.23V and was indicating a possible charging problem however the voltage remained within 0.1V regardless of the electrical load (lights, heated front and rear screen, heated seats, etc.). This used to stress me out but now I just accept it since the car always starts fine, despite doing lots of very short trips.

Really interesting that you should post this, because it matches my update.

Dealer replaced the battery with an AGM. Since then, rather than stay nailed at 14.9V permanently as it was, the voltage ranges between mid 12's and 14.7V (slowly, not jumpy!). This is exactly as it should be with an intelligent charging system. It will measure integrated charge over time and knows when the battery is full. It then lets it drop, say 10%, before topping up again. This regime normally better applied to cars with brake regen, which I am pretty sure I don't have. But none the less, this ranging of charge volts is normal.

Now the odd thing is, the estimated fuel range when has changed since they had the car. It was consistently 386 on refill. Now it's jumped to around 436 on refill. Not concerned, but it suggests to me a software change. I am not convinced that they have not done something in addition to swapping the battery - a hardware or firmware fault in the charging circuits.

I am just glad I persevered with it - they were about to bring it back when I raised the issue for the 3rd time.

Gets more interesting. We do have brake regen. When decelerating, battery charges at 14.7. While on throttle, floats 12 to 13, unless electrical load high, then 13.8 or 14.4.

Technically that is not brake regen, brake regen is when the charging load is such that the alternator/generator retards the vehicle and not the brakes, on the Freelander2 both auto and manual gearbox braking turns the engine which is software set to charge the battery. You can only achieve brake regen on a hybrid vehicle where any retardation uses the electric motor as a generator to achieve a longer electric capability. OK that's picking holes, but the Freelander does have a fairly sophisticated charging system to help it's emission ratings which lowers the VED, green I'm not but saving cash is a hobby though not an OCD one  my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

Last edited by Dartman the one on 24th Oct 2017 5:54 pm. Edited 1 time in total

PEDANT ALERT - proceed at your own risk.

Perhaps I used the wrong term - but it is regenerative charging. The car is loaded by the alternator when you go off throttle. That retards the car faster than would have been the case if the alternator was not loaded, so it produces some added engine braking and the recovered energy goes into the battery. It may not be hugely efficient, but it is a form of brake energy regeneration. But agreed, it's not the action of the brake pedal which creates it, it is coming off throttle and going overrun.

A system that adds regeneration when you hit the brake is more efficient, but produces too much energy for a standard battery. That charges a bigger battery which then drives an electric motor - that is a Hybrid. (The motor is usually the generator too)

All by the by, but now googling I find that Smart Regenerative Charging has been on the FL2 since a mid-life facelift. And going back to where we started this thread, ours was clearly not working when we took delivery of the car, but has now been resolved. Not sure if that is the reason, or the oil change or the Millers, but fuel economy of a long run of 200 miles has improved form 37 to 40mpg.

LOL - I put PENDANT alert the first time !!

We could just get 40mpg on a trip from Scotland to Dover, but apart from a just fill and reset it dropped back to about 37mpg average, strangely out here it will easily get to 40-42 on the 50-60Km trip to the airports, warm weather and a quick up to temperature time may be the reason, Except in town there is no need to do much braking, not much traffic and very low speed limits, the police can be extremely lax or strict depending on your actual speed, the higher over the limit the more revenue collected therefore bonuses and promotion are the incentive  my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.